A conventional water quality sensing system using an actuator and a sensor constantly maintains the magnitude of an input signal generated in the actuator to detect the change of a medium formed by the actuator. A sensing system according to the prior art uses single ended signal scheme and/or a negative feedback configuration for a more stable structure.
For example, when an actuator irradiates a medium containing a substance of which a concentration to be measured with a certain amount of light, a turbidity sensor detects and converts the light transmitted through the medium into an electrical signal to measure the concentration of the substance in the medium.